Configuration.h: Use OVERSAMPLENR in dT_PID definition.

Marlin/Configuration.h

                                   // is more then PID_FUNCTIONAL_RANGE then the PID will be shut off and the heater will be set to min/max.
   #define PID_INTEGRAL_DRIVE_MAX 255  //limit for the integral term
   #define K1 0.95 //smoothing factor within the PID
-  #define PID_dT ((16.0 * 8.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the temperature routine
+  #define PID_dT ((OVERSAMPLENR * 8.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the temperature routine
 
 // If you are using a preconfigured hotend then you can use one of the value sets by uncommenting it
 // Ultimaker